Aircraft arresting systems for arresting the forward motion of a landing aircraft in a limited amount of space, such as during an emergency landing or onto an aircraft carrier deck, are well known. These systems include a device for engaging the landing aircraft such as pendant cables or a net consisting of expandable fabric webbing straps stretched across the path of the incoming aircraft. The engaging device is connected at each of its ends to flexible means such as Nylon webbing or tape, each end of which is in turn, attached to an energy absorbing device called an arresting gear engine. The arresting gear engine is commonly either a friction brake or clutch, or a hydraulic damper.
Aircraft exist in a large range of sizes and weights, and the size and weight of the aircraft to be arrested will generally not be known in advance. Furthermore, the landing velocities of aircraft vary widely, and will likewise generally not be known until the instant of landing. It is imperative that the correct force be used to restrain each aircraft regardless of weight and velocity. If too great a force is applied, the hook (on hook-equipped aircraft) might be ripped off light aircraft. However, the same force may be insufficient to arrest heavy, high velocity aircraft in the available space. The same situation exists with net arrestments. Control of the force applied by the arresting system must be automatic, since the weight and velocity of the aircraft is not known in advance, and the entire period of the arrestment is generally only a few seconds.
Controlling the force applied to the aircraft to achieve the optimum deceleration has proven difficult in practice, particularly when there is a large range of aircraft weights and velocities to be arrested. This is due to, for example, the changes in the geometry of the pendant cable or net and webbing system which occur during the period of the arrestment, the fact that the diameter of the tape wound around the reel gradually decreases during the arrestment as more webbing is payed out, and the fact that lighter aircraft require less arresting force than heavier aircraft to achieve the same rate of deceleration. Further, the arresting force is generally affected by the speed of rotation of the tape reel, which speed changes during the arrestment. Because of all these simultaneous changes, and the fact that the aircraft must be brought to a complete stop in the range of a few seconds, prior art arresting gear systems have been designed for a relatively narrow range of aircraft weights and landing velocities.